Conventionally, an illumination apparatus has been used in the areas such as shops in which a display effect is regarded as important. The illumination apparatus irradiates on a target object, light in which light in a specific wavelength range is reduced, thereby clearly displaying the target. In the illumination apparatus, for example, a band filter is attached to a light source in order to reduce the light in the specific wavelength range.
As an example of such a band filter, there is known a band filter that has a minimum light transmittance in a wavelength range of 500 to 600 nm (see, e.g., Japanese Patent Laid-open Publication No. 2001-66421 (JP2001-066421A)). This band filter has 40% to 95% of the light transmittance in the wavelength range of 500 nm to 600 nm, and 70% of the average light transmittance in the wavelength range of 400 nm to 500 nm and 600 nm to 700 nm adjacent to the above wavelength range.
The band filter aside, there is known a long wavelength cut-off filter which reduces the light having a wavelength longer than a specific wavelength and a short wavelength cut-off filter which reduces the light having a wavelength shorter than a specific wavelength, as an optical member for wavelength control. The long and short wavelength cut-off filter reduce light in a specific wavelength range more specifically than a general band filter. Further, they transmit light in a wavelength range rather than the specific wavelength range.
In the illumination apparatus disclosed in JP2001-66421A, light in a specific wavelength range is reduced by using the filter, but also reduced is light in a wavelength range adjacent to the specific wavelength range. Thus, a necessary light may be reduced, and a sufficient display effect may not be obtained.